Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.83	11.289%	$158.9541	$158.95	$158.95	$159.00
Purchase #2	$88.39	11.362%	$98.4329	$98.43	$98.45	$98.40
Purchase #3	$85.38	10.274%	$94.1519	$94.15	$94.15	$94.20
Purchase #4	$41.28	10.271%	$45.5199	$45.52	$45.50	$45.50
Purchase #5	$57.31	4.771%	$60.0443	$60.04	$60.05	$60.00
Purchase #6	$103.42	9.167%	$112.9005	$112.90	$112.90	$112.90
Purchase #7	$136.47	5.692%	$144.2379	$144.24	$144.25	$144.20
7 purchase totals =	$655.08		$714.2415	$714.23	$714.25	$714.20